Method for immobilizing particles and method for producing particle-immobilized substrate

ABSTRACT

The present invention is a method for immobilizing particles  32  on a first electrode  14  formed on a substrate  12 , including a forming step of forming a particle layer  30  at least on the first electrode  14  and an immobilizing step of immobilizing the particle layer  30  on the first electrode  14  by immersing the substrate  12  in a monomer solution  40  containing an electropolymerizable monomer while a counter electrode  39  is disposed opposite the first electrode  14  with the particle layer  30  formed on the first electrode  14  and applying a potential difference between the first electrode  14  and the counter electrode  39  to electropolymerize the monomer on the first electrode  14.

TECHNICAL FIELD

The present invention relates to a method for immobilizing particles aswell as a method for producing particle-immobilized substrates.

BACKGROUND ART

A method is proposed in the art in which a multilayer film that does noteasily peel from a substrate is prepared by forming a film having achemical group that can be easily immobilized on the substrate on thesubstrate by the Langmuir-Blodgett technique (LB technique) and furtherforming a plurality of films of different materials on the film formedon the substrate (see, for example, Patent Document 1). Also proposed isa method in which a polymer is formed on an electrode with magneticmicroparticles dispersed in the polymer by immersing the electrode in asolution having a polymerizable monomer and magnetic microparticlesdispersed therein and electropolymerizing the monomer (see, for example,Patent Document 2). This method allows a thin film with low density andhigh flexibility to be formed.

-   Patent Document 1: JP 2006-150661 A-   Patent Document 2: JP 06-338432 A

DISCLOSURE OF INVENTION

When, for example, a particle layer is to be formed only on an electrodeformed on a substrate, it may be desirable to firmly immobilize theparticles on the electrode for ease of handling in the subsequent steps.In such cases, with the method of Patent Document 1, a particle layer infilm form is formed not only on the electrode, but also on the otherportion of the substrate; therefore, another method in which no particlelayer is formed on the substrate, such as pattering with a mask orpatterning with a resist, needs to be performed. In addition, the rangeof options, including the chemical groups formed on the substrate andthe film, is limited. Immobilization of LB films is basically due to abond formed by intermolecular force, which is weak and cannot immobilizeparticles on an electrode sufficiently firmly, particularly when theparticle size exceeds the submicron order. In the method of PatentDocument 2, on the other hand, a polymer layer is formed on anelectrode, although the method forms a highly flexible polymer layer onan electrode, rather than firmly immobilizes particles on an electrode.

A primary object of the present invention, which has been made in lightof such problems, is to provide a method for immobilizing particles anda method for producing a particle-immobilized substrate that allowparticles to be immobilized on an electrode more easily and more firmly.

As a result of intensive research for achieving the above primaryobject, the present inventors have found that particles can beimmobilized on an electrode more easily and more firmly by forming aparticle layer on a substrate having an electrode formed thereon andthen forming a polymer on the electrode by electropolymerization usingthe electrode, thus completing the present invention.

A method of the present invention for immobilizing particles is:

a method for immobilizing particles on a first electrode formed on asubstrate, including:

a forming step of forming a particle layer at least on the firstelectrode; and

an immobilizing step of immobilizing the particle layer by immersing thesubstrate in a solution containing an electropolymerizable chemicalwhile a counter electrode is disposed opposite the first electrode withthe particle layer formed on the first electrode and applying apotential difference between the first electrode and the counterelectrode to electropolymerize the chemical on the first electrode.

In addition, a method of the present invention for producing aparticle-immobilized substrate is:

a method for producing a particle-immobilized substrate having particlesimmobilized on a first electrode formed on the substrate, including:

a forming step of forming a particle layer at least on the firstelectrode; and

an immobilizing step of immobilizing the particle layer by immersing thesubstrate in a solution containing an electropolymerizable chemicalwhile a counter electrode is disposed opposite the first electrode withthe particle layer formed on the first electrode and applying apotential difference between the first electrode and the counterelectrode to electropolymerize the chemical on the first electrode.

In the method of the present invention for immobilizing particles andthe method of the present invention for producing a particle-immobilizedsubstrate, the particles can be more firmly immobilized because theparticles are mechanically immobilized by the polymer formed on thefirst electrode by electropolymerization. In addition, even if theparticle layer is formed in the region on the substrate other than thefirst electrode, the particle layer can be easily removed from theregion other than the first electrode without performing, for example,pattering with a mask or patterning with a resist, as in the known art,because the chemical is electropolymerized on the first electrode andthe particles are not firmly immobilized in the region other than thefirst electrode. Accordingly, the particles can be more easily and morefirmly immobilized on the electrode.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram showing an example of a method of thisembodiment for producing a particle-immobilized substrate 10.

FIG. 2 is an explanatory diagram showing another example of the methodof this embodiment for producing the particle-immobilized substrate 10.

FIG. 3 is an explanatory diagram illustrating a series of steps ofproducing a stack 50.

FIG. 4 shows explanatory diagrams of other examples of theparticle-immobilized substrate 10: FIG. 4( a) shows an example with amultilayer pattern of cubic particles; FIG. 4( b) shows an example witha monolayer pattern of cubic particles; FIG. 4( c) shows an example withceramic particles combined by firing; and FIG. 4( d) shows an examplewith a pattern of immobilized layer 34 based on an electrode pattern.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will now be described withreference to the drawings. FIGS. 1 and 2 are explanatory diagramsshowing examples of a method of this embodiment for producing aparticle-immobilized substrate 10. As shown in the bottom stage of FIG.1, the particle-immobilized substrate 10 includes a substrate 12, afirst electrode 14 formed on the substrate 12, and an immobilized layer34 formed on the first electrode 14 and having particles 32 immobilizedwith a resin 42. The particle-immobilized substrate 10 may befabricated, for example, as an intermediate (part) to a device having anelectrode formed on a substrate. The particle-immobilized substrate 10may be a substrate including an electrode on which particles havingproperties such as piezoelectric properties, ferroelectric properties,magnetic properties, thermoelectric properties, ion conductivity, oroptical properties are immobilized. That is, examples of devices includepiezoelectric/electrostrictive devices, ferroelectric devices, magneticdevices, thermoelectric transducers, ion-conductive devices, and opticaldevices. In addition, this particle-immobilized substrate 10 may be usedas-is or may be fabricated, for example, as an intermediate to a devicehaving another electrode formed on the immobilized layer 34. That is,the particle-immobilized substrate 10 may be fabricated as a devicehaving a structure in which a layer of particles is held betweenelectrodes, examples of which include piezoelectric/electrostrictivedevices, ferroelectric devices, thermoelectric transducers, andion-conductive devices. In this case, the first electrode 14 formed onthe substrate 12 can be used as-is for such devices.

The substrate 12 may be any substrate having an insulating surface onwhich a conductive electrode can be formed, such as one or more ofglass, single crystal, ceramic, resin, and insulator-coated metalsubstrates. Examples of glass substrates include quartz and alkali-freeglass. Examples of single crystal substrates include silicon, galliumarsenide, silicon carbide, and alumina. Examples of ceramic substratesinclude stabilized zirconium oxide, aluminum oxide, magnesium oxide,mullite, aluminum nitride, and silicon nitride. Examples of resinsubstrates include epoxy resins and polyester resins. Examples ofinsulator-coated metal substrates include metals, such as stainlesssteel and aluminum, coated with an insulating resin.

The first electrode 14 is formed of a conductive material. The materialof the first electrode 14 may be at least one or more selected from thegroup consisting of platinum, palladium, ruthenium, gold, silver, alloysthereof, and conductive polymers. In the case where theparticle-immobilized substrate 10 is to be fired later, platinum or analloy mainly containing platinum is preferred as the material of thefirst electrode 14 because it has high heat resistance in firing. Inaddition, the pattern of the first electrode 14 may be formed by anymethod such as evaporation, sputtering, screen printing, electrolessplating, or interfacial monomer polymerization.

The particles 32 may be formed of, for example, glass, ceramic, resin,or insulator-coated metal. Preferably, the particles 32 have insulationproperties so that the monomer of the resin 42 is electropolymerized atthe interface of the first electrode 14. More preferably, for example,the particles 32 are ones that exhibit improved properties when alignedor oriented on the first electrode 14. In this case, the properties ofthe immobilized layer 34 can be further improved by the method of thepresent invention for immobilizing particles. The particles 32 used maybe, for example, one or more of particles having piezoelectricproperties, particles having ferroelectric properties, particles havingmagnetic properties, particles having thermoelectric properties,particles having ion conductivity, and particles having opticalproperties. Particles having such properties can deliver the sameproperties in, for example, the resulting particle-immobilized substrate10 or device. Examples of particles having piezoelectric propertiesinclude lead zirconate titanate (PZT: Pb(Zr,Ti)O₃), lithium niobate(LiNbO₃), lithium tantalate (LiTaO₃), quartz crystal (SiO₂), zinc oxide(ZnO), lithium tetraborate (Li₂B₄O₇), langasite (La₃Ga₅SiO₁₄), aluminumnitride (AlN), and polyvinylidene fluoride (PVDF). Examples of particleshaving ferroelectric properties include BaTiO₃, Pb(Zr,Ti)O₃ (PZT),SrBi₂Ta₂O₉ (SBT), (Bi,La)₄Ti₃O₁₂ (BLT), and BaBi₄Ti₄O₁₄. Examples ofparticles having magnetic properties include ferrite (FeO.Fe₂O₃,MnO.Fe₂O₃, NiO.Fe₂O₃, and CoO.Fe₂O₃. Examples of particles havingthermoelectric properties include bismuth-tellurium compound,lead-tellurium alloy, silicon-germanium alloy, cobalt-antimony compound,and zinc-antimony compound. Examples of particles having ionconductivity include stabilized zirconia, β-alumina, andperfluorosulfonic acid polymers. Examples of particles having opticalproperties include particles containing one of indium oxide, zinc oxide,and tin oxide, such as Zn—In—Sn—O-based materials, Zn—In—O-basedmaterials, In—Sn—O-based materials, and Zn—In—Sn—O-based materials. Theparticles 32 may be formed in various shapes, including a sphere, cube,tetrahedron, octahedron, bar, and plate. Among others, a sphere, cube,tetrahedron, and octahedron are preferred to form a dense body becausethey allow the filling factor of the particles to be increased.

The resin 42, which is formed by electropolymerization, may be a polymerof, for example, a vinyl monomer such as styrene or N-vinylcarbazole, anaromatic ring compound such as aniline or phenol, or a heterocycliccompound such as pyrrole, thiophene, or furan. Examples ofelectropolymerization include polymerization reaction caused through theformation of radical cations or radical anions, polymerization reactioncaused by reactive species such as cations, anions, or free radicalsformed by oxidation or reduction of a coexisting supporting electrolyteor additive, and chain polymerization or successive polymerizationdepending on the type of monomer. Of these, the resin 42 is preferably apolymer of, for example, pyrrole, an alkylpyrrole, aminopyrrole,aniline, thiophene, an alkylthiophene, or a thiophene derivative. Theresin 42 may also be a polymer formed by adding a sodiumalkylbenzenesulfonate such as sodium p-toluenesulfonate, sodiumethylbenzenesulfonate, or sodium dodecylbenzenesulfonate as an oxidantto induce electropolymerization.

Next, the method for producing the particle-immobilized substrate 10will be described. For example, as shown in FIG. 1, the method forproducing the particle-immobilized substrate 10 can include (1) afirst-electrode forming step of forming the first electrode 14 on thesubstrate 12, (2) a particle-layer forming step of forming the particlelayer 30 on the first electrode 14, (3) an immobilizing step ofimmobilizing the particle layer 30 on the first electrode 14, and (4) acleaning step of cleaning off the particles 32 from the region on thesubstrate 12 other than the first electrode 14. Alternatively, as shownin FIG. 2, the method for producing the particle-immobilized substrate10 can include (1) the electrode-forming step, (2) a particle-layerforming step of forming the particle layer 30 by immersing the substrate12 in a slurry monomer solution 44 containing the particles 32 and themonomer of the resin 42, (3) an immobilizing step of forming the resin42 on the first electrode 14 in the slurry monomer solution 44 byelectropolymerization, (4) the cleaning step, and (5) after theimmobilizing step and before the cleaning step, a repolymerizing step ofimmersing the substrate 12 after the immobilizing step in a monomersolution 40 containing an electropolymerizable monomer and furtherforming the resin 42 on the first electrode 14 by electropolymerization.

(1) First-Electrode Forming Step

First, a process in which the first electrode 14 is formed on thesubstrate 12 is performed (the first stage of FIG. 1). The substrate 12on which the first electrode 14 is to be provided may be formed of, forexample, glass, single crystal, ceramic, resin, or insulator-coatedmetal, as described above. The first electrode 14 may be formed of oneor more of conductive inorganic compounds such as metals and oxides andconductive polymers as described above. The first electrode 14 may beformed by, for example, evaporation, sputtering, or monomerpolymerization reaction of the electrode material. The first electrode14 can also be formed in the desired pattern on the substrate 12 bypreparing a paste of the electrode material and coating the substrate 12with the paste by, for example, doctor blade coating or screen printing,or by electroless plating. The shape and thickness of the firstelectrode 14 may be appropriately selected.

(2) Particle-Layer Forming Step

Next, the particle layer 30, which is a layer of the particles 32, isformed at least on the first electrode 14 formed on the substrate 12having the first electrode 14 formed thereon. The particles 32 used maybe formed of, for example, glass, ceramic, resin, or insulator-coatedmetal, as described above. In addition, particles havingpiezoelectric/electrostrictive properties, particles havingferroelectric properties, particles having magnetic properties,particles having thermoelectric properties, particles having ionconductivity, or particles having optical properties may be used. Theparticle layer 30 may be formed by any method that forms one that can besubjected to the subsequent immobilizing step. For example, the particlelayer 30 may be formed directly without immersing the substrate 12 in asolution, as shown in the second stage of FIG. 1, or may be formed onthe first electrode 14 by immersing the substrate 12 in a solution(slurry) containing the particles 32, as shown in the second stage ofFIG. 2. The former method may be, for example, one or more of spraycoating, spin coating, and doctor blade coating. The latter method maybe, for example, one or more of a method in which the substrate 12 isimmersed and left standing in a slurry having the particles 32 dispersedtherein until they settle down, the LB technique, in which the substrate12 is immersed in and lifted out of the liquid phase with the particles32 aligned at the interface thereof, electrophoresis, and dipping. Suchmethods allow the particle layer 30 to be relatively easily formed onthe first electrode 14. Of these, the method in which the substrate 12is immersed in a slurry until the particles 32 settle down is preferablyused because the subsequent immobilizing step (electropolymerization ofpolymer) can be easily entered. The particle layer 30 can be moredensely filled by applying, for example, mechanical vibrations, acousticwaves, heat, light, or a magnetic field during the formation thereof. Inaddition, because the particle layer 30 is immersed in a solution in theimmobilizing step, it may be strengthened by drying or heating after theformation thereof.

(3) Immobilizing Step

Next, a process is performed in which the immobilized layer 34 havingthe particle layer 30 immobilized therein is formed by immersing thesubstrate 12 in the monomer solution 40 containing theelectropolymerizable chemical (monomer) while a counter electrode 39 isdisposed opposite the first electrode 14 with the particle layer 30formed on the first electrode 14 and applying a potential differencebetween the first electrode 14 and the counter electrode 39 toelectropolymerize the monomer on the first electrode 14. Byelectropolymerizing the monomer on the first electrode 14, the particles32 can be immobilized only on the first electrode 14. At this time, forexample, as shown in FIG. 2, the particle layer 30 may be formed in theparticle-layer forming step by immersing the substrate 12 in the slurrymonomer solution 44 containing the particles 32 and theelectropolymerizable monomer and may then be immobilized with the resin42 in the immobilizing step by electropolymerizing the monomer on thefirst electrode 14 in the slurry monomer solution 44. This is preferablein that the immobilizing step can be performed immediately after theformation of the particle layer 30 and is therefore easier to perform.Alternatively, for example, the particle layer 30 may be formed on thefirst electrode 14 in the particle-layer forming step by immersing andlifting the substrate 12 in and out of the slurry monomer solution 44with the particles 32 floating in film form in the surface thereof whilethe counter electrode 39 is disposed opposite the first electrode 14 andmay then be immobilized with the resin 42 in the immobilizing step byapplying a potential difference between the first electrode 14 and thecounter electrode 39 to electropolymerize the monomer on the firstelectrode 14 when the substrate 12 is lifted. By doing so, the formationof the particle layer 30 and the immobilization of the particles 32 canbe performed substantially at the same timing to form a relatively thinparticle layer. Here, the monomer solution 40 may be a solution in whichan electropolymerizable monomer is dissolved and/or dispersed. Asdescribed above, the monomer used may be a vinyl monomer, aromatic ringcompound, or heterocyclic compound, and is preferably, for example,pyrrole, an alkylpyrrole, aminopyrrole, aniline, thiophene, analkylthiophene, or a thiophene derivative. The solvent used may beappropriately selected from water and organic solvents, depending on themonomer. In particular, an aqueous pyrrole solution is preferably usedbecause it can be handled as a solvent. In addition, a sodiumalkylbenzenesulfonate such as sodium p-toluenesulfonate, sodiumethylbenzenesulfonate, or sodium dodecylbenzenesulfonate may be added tothe solution as an oxidant to induce electropolymerization. Theelectropolymerization may be performed by disposing a counter electrodein the monomer solution 40 and controlling, for example, the electricalconditions (voltage and current) and the treatment time depending on thediameter of the particles immobilized and the thickness and size of theparticle layer. In this way, the immobilized layer 34 having theparticles 32 immobilized with the resin 42 formed byelectropolymerization can be formed on the first electrode 14. Theimmobilized layer 34 is more firmly formed on the first electrode 14because the resin 42 mechanically immobilizes the particles 32 byfilling the gaps therebetween.

(4) Cleaning Step

Next, a process is performed in which the particle layer 30 is removedfrom the region other than the first electrode 14 on the substrate 12 onwhich the immobilized layer 34 is formed. The particles not immobilizedwith the resin 42 formed by electropolymerization can be removed byrunning water cleaning or supersonic cleaning. In this way, theparticle-immobilized substrate 10 having the particles 32 immobilized onthe first electrode 14 with the resin 42 can be obtained by an easierprocess.

(5) Repolymerizing Step

As shown in the fourth stage of FIG. 2, after the immobilizing step andbefore the cleaning step, a process may be performed in which themonomer is electropolymerized again by immersing the substrate 12 havingthe particle layer 30 formed thereon, in the solution containing themonomer but not containing the particles 32 and applying a potentialdifference between the first electrode 14 and the counter electrode 39.By doing so, more polymer can be formed in the immobilized layer 34,thus allowing the upper layer of particles 32 to be easily removed toobtain a particle-immobilized substrate 10 having an immobilized layer34 including a monolayer of particles 32 formed on the first electrode14. When, for example, particles 32 of submicrons to several microns insize are immobilized with a conductive polymer, electropolymerizationcan be performed again in a conductive monomer solution to form animmobilized layer 34 including a monolayer of particles 32. The cleaningstep described above may be performed after the repolymerizing step, ormay be performed before and after the repolymerizing step.

In the method for producing the particle-immobilized substrate 10 ofthis embodiment described in detail above, because the particles 32 aremechanically immobilized with the resin 42 formed byelectropolymerization of the resin 42, the immobilized layer 34 isfirmer, and the range of options of the types of substrate 12, firstelectrode 14, and particles 32 can be significantly broadened. Inaddition, the use of electropolymerization provides an easier processfor forming the immobilized layer 34 only on the first electrode 14without performing, for example, pattering with a mask or patterningwith a resist, as in the known art. In addition, because the immobilizedlayer 34 is formed by electropolymerization after the formation of theparticle layer 30 on the first electrode 14, a denser immobilized layer34 can be formed. In addition, the first electrode 14 can be used toform the immobilized layer 34 and later, for example, to form a devicehaving the immobilized layer 34 held between a plurality of electrodes.In this embodiment, an example of a method of the present invention forimmobilizing particles also becomes apparent from the description of themethod for producing the particle-immobilized substrate 10.

It is to be understood that the present invention is not limited to theembodiment described above in any aspect, but can be practiced invarious manners within the technical scope of the present invention.

For example, whereas the method of the embodiment described above is amethod for producing the particle-immobilized substrate 10 having theimmobilized layer 34 formed on the first electrode 14, it may include,as shown in FIG. 3, (6) a second-electrode forming step of forming asecond electrode 16 on the immobilized layer 34 of theparticle-immobilized substrate 10 and (7) a firing step of firing theparticle-immobilized substrate 10 having the second electrode 16 formedthereon. That is, the method may be a method for producing a stack 50(device) having a formed layer 36 held between the first electrode 14and the second electrode 16. FIG. 3 is an explanatory diagramillustrating the series of steps of producing the stack 50. In thesecond-electrode forming step, the same process as the first-electrodeforming step described above can be used. In addition, in the firingstep, firing is performed under the conditions matching the propertiesof the substrate 12, the first electrode 14, the particles 32, the resin42, etc. In the firing step, for example, the particle-immobilizedsubstrate 10 may be fired at a temperature at which the particles 32sinter or at a temperature at which the resin 42 disappears after thefiring, and accordingly the materials of the substrate 12 and the firstelectrode 14 may be selected taking into account heat resistance. Inaddition, the firing step may be performed after the formation of thefirst electrode 14, after the formation of the immobilized layer 34,after the formation of the second electrode 16, or after one or more ofthose steps. By forming a first electrode 14 of a conductive polymer inthe first electrode forming step on a substrate 12 that can be fired,providing thereon an immobilized layer 34 that can be fired, and firingthe particle-immobilized substrate 10, the first electrode 14 disappearsafter the firing, thus leaving a stack having the formed layer 36 formeddirectly on the substrate 12 without the first electrode 14therebetween.

Whereas the method of the embodiment described above for producing theparticle-immobilized substrate 10 may include the electrode-formingstep, the particle-layer forming step, the immobilizing step, thecleaning step, and the repolymerizing step, it may include only theparticle-layer forming step and the immobilizing step.

Whereas the particle-immobilized substrate 10 has been described withreference to FIGS. 1 and 2 in the embodiment described above, variousforms may be employed, as shown in FIG. 4. FIG. 4 shows explanatorydiagrams of other examples of the particle-immobilized substrate 10:FIG. 4( a) shows an example with a multilayer pattern of cubicparticles; FIG. 4( b) shows an example with a monolayer pattern of cubicparticles; FIG. 4( c) shows an example with ceramic particles combinedby firing; and FIG. 4( d) shows an example with a pattern of immobilizedlayer 34 based on an electrode pattern. As shown, the particles 32 maybe formed in a rectangular shape, may be formed either as a monolayer oras a multilayer, may be fired to form a ceramic layer, and may have apattern such as an interdigital pattern.

EXAMPLES

Actual examples of the particle-immobilized substrate 10 of the presentinvention will now be described.

Example 1

A platinum pattern having a width of 1 mm, a length of 40 mm, and athickness of 10 μl was formed on a zirconia substrate having a size of30 mm×30 mm and a thickness of 150 μm by screen printing and was firedat 1,350° C. using an electric furnace to form a′ platinum electrode(first electrode) on the substrate. In addition, an aqueous pyrrolesolution was prepared by adding sodium dodecylbenzenesulfonate andpyrrole to 30 mL of pure water such that the concentration was 0.01mol/L. The prepared aqueous solution was poured into a beaker, and byweight of cubic PZT particles prepared by hydrothermal synthesis andhaving a particle size of 3 μm were added to the aqueous solution andwere dispersed with a homogenizer to prepare a suspension (slurrymonomer solution). The zirconia substrate described above was thenplaced on the bottom of the beaker containing the solution and was leftstanding for ten minutes until the PZT particles settled down. Astainless steel counter electrode was then disposed at an interelectrodedistance of 1 mm parallel to the substrate, a power supply was connectedsuch that the platinum electrode on the substrate was positive inpolarity and the counter electrode was negative in polarity, and atriangular wave at 2 Hz with a peak voltage of 5 V was applied 30 timesto synthesize polypyrrole on the platinum electrode. The substrate onwhich the polypyrrole was formed was shaken in the aqueous solution toroughly remove excess particles and was then subjected to ultrasoniccleaning in pure water to remove the PZT particles deposited in theregion other than the platinum electrode. In this way, aparticle-immobilized substrate having an immobilized layer including PZTparticles immobilized in film form only on the platinum electrode wasobtained as Example 1. The particle size of the PZT particles is themedian size (D50) measured with the dynamic light scattering particlesize analyzer Zetasizer Nano nano-ZS manufactured by Spectris Co., Ltd.using water as a dispersion medium. In addition, the ultrasonic cleaningfor removing the PZT particles was performed using an ultrasonic cleaner(UT-106, manufactured by Sharp Corporation) at 40 kHz for one minute.

Example 2

The PZT particles were immobilized by synthesizing polypyrrole on theplatinum electrode as in Example 1, and the substrate was shaken in theaqueous solution to roughly remove excess particles. The substrate and acounter electrode disposed opposite the first electrode on the substratewere then immersed in another aqueous pyrrole solution having no PZTparticles suspended therein, and a triangular wave at 2 Hz with a peakvoltage of 5 V was applied 30 times to further synthesize polypyrrole onthe particle-immobilized substrate. By cleaning the substrate with purewater after the synthesis, the PZT particles deposited in the regionother than the platinum electrode and the particles deposited on theparticles immobilized on the platinum electrode could be removed, thusobtaining a particle-immobilized substrate having a monolayer of PZTparticles immobilized in film form only on the first electrode asExample 2.

Example 3

A gold electrode (first electrode) having a width of 1 mm, a length of40 mm, and a thickness of 150 nm was formed on a glass substrate havinga size of 30 mm×30 mm and a thickness of 2 mm by DC sputtering. Inaddition, an aqueous pyrrole solution was prepared by adding sodiumdodecylbenzenesulfonate and pyrrole to 30 mL of pure water such that theconcentration was 0.01 mol/L. The prepared aqueous solution was pouredinto a beaker, and 1% by volume of spherical polystyrene beads (3200A,manufactured by Moritex Corporation) having a particle size of 200 nmwere added to the aqueous solution and were dispersed with a homogenizerto prepare a suspension (slurry monomer solution). The glass substratedescribed above was then placed on the bottom of the beaker containingthe solution and was left standing for ten minutes until the polystyreneparticles settled down. A stainless steel counter electrode was thendisposed at an interelectrode distance of 1 mm parallel to thesubstrate, a power supply was connected such that the gold electrode onthe substrate was negative in polarity and the counter electrode waspositive in polarity, and a triangular wave at 2 Hz with a peak voltageof 5 V was applied 30 times to synthesize polypyrrole on the goldelectrode. The substrate on which the polypyrrole was formed was shakenin the aqueous solution to roughly remove excess particles and was thensubjected to ultrasonic cleaning in pure water as in Example 1 to removethe polystyrene particles deposited in the region other than the goldelectrode. In this way, a particle-immobilized substrate having thespherical polystyrene beads immobilized in film form only on the goldelectrode was obtained as Example 3.

Example 4

A pair of opposing interdigital gold electrodes (first electrode andcounter electrode) having a thickness of 150 nm was formed on a glasssubstrate having a size of 30 mm×30 mm and a thickness of 2 mm by DCsputtering. In addition, an aqueous pyrrole solution was prepared byadding sodium dodecylbenzenesulfonate and pyrrole to 30 mL of pure watersuch that the concentration was 0.01 mol/L. One percent by volume ofspherical polystyrene beads having a particle size of 200 nm weredispersed in isopropyl alcohol, and the dispersion was added dropwise tothe aqueous pyrrole solution. Thus, the isopropyl alcohol was dissolvedin water to allow the polystyrene beads to float in the surface of theaqueous pyrrole solution. As the glass substrate and the counterelectrode were immersed in the aqueous solution and were lifted in anoblique direction, the polystyrene beads were lifted together with thesubstrate (LB technique). A power supply was connected such that one ofthe pair of gold electrodes on the substrate was negative in polarityand the other was positive in polarity, and a triangular wave at 2 Hzwith a peak voltage of 5 V was applied when the substrate was lifted,thus immobilizing the spherical polystyrene beads in film form only onthe interdigital gold electrodes. By cleaning the substrate with purewater after the synthesis, the PZT particles deposited in the regionother than the gold electrodes and the particles deposited on theparticles immobilized on the gold electrodes were removed, thusobtaining a particle-immobilized substrate as Example 4.

Comparative Example 1

Cubic PZT particles prepared by hydrothermal synthesis and having aparticle size of 3 μm were coated with latex, were suspended inisopropyl alcohol, and were added dropwise to pure water so as to floatin the surface thereof. A glass substrate having gold electrodes formedthereon, prepared as in Example 4, was then lifted out of the solutionin which the PZT particles floated (LB technique), thus obtaining asubstrate having the PZT particles deposited thereon as ComparativeExample 1.

Peel Test

A test for evaluating Examples 1 to 4 and Comparative Example 1 foradhesion was carried out. The test evaluated the peel rate, where it wasdetermined how the coverage of the particles on the first electrodebefore peel treatment changed after the peel treatment. The peeltreatment was performed using the above ultrasonic cleaner in water at40 kHz for one minute. In addition, the coverage (the proportion of theparticles covering the electrode per unit area) was determined byexamining the surface of the first electrode having the immobilizedlayer formed thereon using a scanning electron microscope (JSM-7000F,manufactured by JEOL Ltd.) and digitizing the area covered by theparticles per electrode area by image analysis. In addition, the peelrate was determined by the expression (A−B)/A×100%), where A is thecoverage of the particles on the first electrode before the peeltreatment and B is the coverage after the peel treatment.

Test Results

Table 1 shows the coverage (%) of the particles on the first electrodebefore the peel treatment, the coverage (%) after the peel treatment,and the peel rate (%) for Examples 1 to 4 and Comparative Example 1. Asis obvious from Table 1, whereas the particle layer of ComparativeExample 1 peeled off noticeably and was turned cut to be unsuccessfullyimmobilized, the particle layer of any of the samples of Examples hadhigh coverage and was turned out to be significantly resistant topeeling. In addition, it was assumed that the particles may be providedon the first electrode by any method, such as by allowing the particlesto settle down on the electrode or by the LB technique. In addition, itturned out that the particles can be firmly immobilized irrespective ofthe materials of the particles, the substrate, and the electrode in themethods of Examples 1 to 4 for immobilizing particles on an electrode byelectropolymerization. It also turned out that an immobilized monolayercan be easily formed by electropolymerization after the formation of animmobilized layer.

TABLE 1 Coverage A Coverage B Peel Rate after before peel after peelpeel treatment treatment (%) treatment (%) (A-B)/A × 100(%) EXAMPLE 1 9694 2.1 EXAMPLE 2 90 90 0.0 EXAMPLE 3 92 91 1.1 EXAMPLE 4 89 88 1.1COMPARATIVE 87 2 97.7 EXAMPLE 1

This application claims priority to Japanese Patent Application No.2009-21840 filed on Feb. 2, 2009, the entire contents of which areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

The present invention is applicable to fields involving immobilizingparticles on an electrode, including the ceramic industry.

1. A method for immobilizing particles on a first electrode formed on asubstrate, comprising: a forming step of forming a particle layer atleast on the first electrode; and an immobilizing step of immobilizingthe particle layer by immersing the substrate in a solution containingan electropolymerizable chemical while a counter electrode is disposedopposite the first electrode with the particle layer formed on the firstelectrode and applying a potential difference between the firstelectrode and the counter electrode to electropolymerize the chemical onthe first electrode.
 2. The method for immobilizing particles accordingto claim 1, wherein the particle layer is foamed on the first electrodein the forming step by immersing the substrate in a solution containingthe particles.
 3. The method for immobilizing particles according toclaim 1, wherein the particle layer is formed in the forming step byimmersing the substrate in a solution containing the particles and theelectropolymerizable chemical; and the particle layer is immobilized inthe immobilizing step by electropolymerizing the chemical on the firstelectrode in the solution containing the particles and theelectropolymerizable chemical.
 4. The method for immobilizing particlesaccording to claim 1, wherein the particle layer is formed on the firstelectrode in the forming step by immersing and lifting the substrate inand out of a solution containing the particles and theelectropolymerizable chemical while the counter electrode is disposedopposite the first electrode; and the chemical is electropolymerized onthe first electrode in the immobilizing step by applying a potentialdifference between the first electrode and the counter electrode whenthe substrate is lifted.
 5. The method for immobilizing particlesaccording to claim 1, comprising: after the immobilizing step, arepolymerizing step of immersing the substrate having the particlesimmobilized thereon in a solution containing an electropolymerizablechemical and applying a potential difference between the first electrodeand the counter electrode to electropolymerize the chemical on the firstelectrode.
 6. A method for producing a particle-immobilized substratehaving particles immobilized on a first electrode formed on thesubstrate, comprising: a forming step of forming a particle layer atleast on the first electrode; and an immobilizing step of immobilizingthe particle layer by immersing the substrate in a solution containingan electropolymerizable chemical while a counter electrode is disposedopposite the first electrode with the particle layer formed on the firstelectrode and applying a potential difference between the firstelectrode and the counter electrode to electropolymerize the chemical onthe first electrode.
 7. The method for producing a particle-immobilizedsubstrate according to claim 6, wherein the particle layer is formed onthe first electrode in the fanning step by immersing the substrate in asolution containing the particles.
 8. The method for producing aparticle-immobilized substrate according to claim 6, wherein theparticle layer is formed in the forming step by immersing the substratein a solution containing the particles and the electropolymerizablechemical; and the particle layer is immobilized in the immobilizing stepby electropolymerizing the chemical on the first electrode in thesolution containing the particles and the electropolymerizable chemical.9. The method for producing a particle-immobilized substrate accordingto claim 6, wherein the particle layer is formed on the first electrodein the forming step by immersing and lifting the substrate in and out ofa solution containing the particles and the electropolymerizablechemical while the counter electrode is disposed opposite the firstelectrode; and the chemical is electropolymerized on the first electrodein the immobilizing step by applying a potential difference between thefirst electrode and the counter electrode when the substrate is lifted.10. The method for producing a particle-immobilized substrate accordingto claim 6, comprising: after the immobilizing step, a reimmobilizingstep of immersing the substrate having the particles immobilized thereonin a solution containing an electropolymerizable chemical and applying apotential difference between the first electrode and the counterelectrode to electropolymerize the chemical on the first electrode.